1. Field of the Invention
This invention relates to a valve insertion method without stopping passage of fluid, and a cutting tool.
2. Description of the Prior Art
A valve insertion method comprising drilling a hole in an already-installed pipe (or existing pipe) in a non-water-flow-stopping state, and inserting a valve in the hole thus cut in the already-installed pipe in a line including the same pipe has heretofore been known.
FIGS. 15(a) and 15(b) shows an outline of a conventional valve insertion method disclosed in U.S. Pat. No. 4,516,598.
According to the conventional techniques shown in these drawings, an already-installed pipe 1 is enclosed with a sealing case 800. The sealing case 800 houses a hole saw 802 and a gate 804 therein in advance. A circular opening is then drilled in the already-installed pipe 1 with the hole saw 802. After the opening is drilled, the sealing case 800 is turned as shown by arrows 850 in FIG. 15(a), and the gate 804 is thereafter inserted into the circular opening 803 shown in FIG. 15(b).
The conventional techniques of FIGS. 15(a), (b) enable the insertion of the valve after the completion of the pipe cut-off operation to be carried out speedily. However, in the conventional techniques of FIGS. 15(a), (b), the dimensions of the sealing case 800 increase because it is necessary that the hole saw 802 having the dimensions of which are equal to those of the gate 804 to be inserted is housed in the sealing case 800.
FIG. 16 shows an outline of a conventional valve insertion method disclosed in U.S. Pat. No. 5,611,365 and International Patent Laid-Open W097/31207.
In the method shown in this drawing, an already-installed pipe 1 is enclosed with a sealing case 600 first. A gate 601 is then turned with the sealing case 600 to cut-off the already-installed pipe 1 with a cutting tool 602 fixed to a free end of the gate 601. According to the conventional method described above, the dimensions of the sealing case 600 decrease because the cutting tool 602 has small dimensions. However, since the cutting tool 602 is fixed to the gate 601, the leakage of water is not perfectly prevented. The already-installed pipe 1 is cut-off with a tip type cutting tool 602. Therefore, in order to cut into an already-installed pipe 1 comprising a cast iron pipe or a steel pipe, the sealing case 600 has to be turned many times, so that it takes much time to cut-off the pipe.
U.S. Pat. 5,732,728 discloses a valve insertion method using an assembly provided with a rotary valve casing, a cutting assembly and a gate assembly. According to the conventional techniques, the gate assembly is fixed in place of the cutting assembly after a grooving operation is carried out, so that the dimensions of an apparatus decrease. However, in this prior art method, it is necessary to carry out an operation for replacing the cutting assembly with the gate assembly by opening and closing a seal means, so that the operations take much time.